Sealing device

ABSTRACT

A high performance sealing device having an excellent pressure resistance and realizing a prevention of damage. The sealing device usable at a working pressure of 0 to 2 MPa, and not damaged. even if the pressure of high-pressure fuel of 5 MPa or higher is applied thereto, wherein high pressure fuel on the high pressure side H is sealed by a first seal part  2,  oil from a cam side on a low pressure side L is sealed by a second seal part  3,  and the fuel slightly leaked due to failure of scraping at the first seal part is sealed by the second seal part to form a dual seal structure, and a resin ring  21  coming into slidable sealing contact with a shaft  10  is used in the first seal part  2,  whereby abnormal abrasion does not occur even when fuel having less lubricity is used, and the durability of the seal is increased.

This is a divisional application of application Ser. No. 10/479,417,filed Apr. 13, 2004.

TECHNICAL FIELD

The present invention relates to a sealing device to be used, forexample, as seal for reciprocating movement for a high-pressure fuelpump for pressurizing fuel to a high pressure.

BACKGROUND ART

In recent years, in diesel engines or in gasoline engines, those ofin-cylinder direct injection system in which fuel at high pressure isdirectly injected in a cylinder for combustion have been developed forimproved performance such as fuel-efficient, high output, and so on.

In such an engine of in-cylinder direct injection system requires ahigh-pressure fuel pump for pressurizing fuel to a high pressure, andsuch high-pressure fuel pump is provided with a sealing device forreciprocating movement in which high sealing property is required.

One of sealing devices for reciprocating movement in the related art isshown in FIG. 9. A sealing device 101 shown in FIG. 9 is employed forthe purpose of sealing high-pressure fuel supplied from a high-pressurefuel pump used for an engine, which performs fuel injection, to thehigh-pressure side H, which is the side to be sealed, of a shaft 110reciprocating in the axial direction.

In FIG. 9, the sealing device 101 is disposed at the end of a housing111, so as to seal high-pressure fuel (gasoline, light oil, and so on),which is an object to be sealed, flown from the high-pressure side H andpassed through a sliding portion of a shaft guiding portion of thehousing 111. Also, sealed on the low-pressure side L of the sealingdevice 101 is oil intended for lubrication and cooling.

In addition, the sealing device 101 includes a metal ring 102 having acylindrical portion 102 a to be fitted on the outer periphery of an endof the housing 111, and a first and a second seal lips 103, 104 formedof rubber-like resilient body, each extending from an inwardly directedflange section 102 b provided at the end of the low-pressure side L ofthe cylindrical portion 102 a of the metal ring 102 toward thehigh-pressure side H and the low-pressure side L for sliding on theshaft 110.

However, in the sealing device in the related art shown in FIG. 9, inorder to prevent fuel leakage due to excessive abrasion of the seal lip,damage of the rubber-like resilient body, and so on, which may be causedby increase in the pressure of the high-pressure fuel, it has beennecessary to construct the pump in such a manner that the pressure ofthe high-pressure fuel relating to the sealing device is limitednormally to 0 to 0.6 MPa.

Therefore, the rubber-like resilient body is thin and when it issubjected to the pressure of the high-pressure fuel of 1 MPa or higher,it may be broken abruptly upon operation.

Since the used fuel has no lubricity, the more the pressure of thehigh-pressure fuel increases, the more the seal lip is abraded in anabnormal manner, and thus fuel leakage is more likely to occur.

In the case of fuel containing alcohol, the rubber-like resilient bodyis swelled, and thus is lowered in hardness and strength, whereby abruptbreakage upon operation, or fuel leakage due to decrease of tighteningmargin of the seal lip may occur.

In addition, since the device is bulky, space saving could not beachieved.

On the other hand, elimination of a drain port is contemplated forsimplifying the pump construction. However, since elimination of thedrain port may increase the pressure of the high-pressure fuel, itcannot be eliminated for limiting the working pressure of thehigh-pressure fuel to 0-0.6 MPa, and hence simplification of the pumpconstruction cannot be achieved.

In view of such problems in the related art as described above, it is anobject of the present invention to provide a high-performance sealingdevice which is superior in pressure-resistance, and thus can realizeprevention of breakage.

DISCLOSURE OF INVENTION

In order to achieve the object described above, the present invention isa sealing device for sealing an annular gap formed between two opposingreciprocating surfaces, characterized by including a first sealing parthaving a resin sealing member coming into slidable sealing contact withone of the opposed surfaces and an urging member for urging the resinsealing member toward the one of the opposed surfaces, and

a second sealing part disposed on the side of the first sealing partopposite from the side to be sealed.

Therefore, dual-sealing structure in which slight leakage due to failureof scraping at the first sealing part is sealed by the second sealingpart is realized, and thus it can be used at the working pressure of 0-2MPa, and moreover, it is prevented from breaking even when beingsubjected to the pressure of the high-pressure fuel at 5 MPa or higher.

Also, since a resin sealing member, which comes into slidable sealingcontact with the one of the opposed surfaces, is used in the firstsealing part, even when fuel having less lubricity is used, abnormalabrasion is prevented and thus durability of the seal is improved.

In addition, even when a fuel containing alcohol is used, swellinghardly occurs at the first sealing part since the sealing member used ismade of resin, and the urging member is prevented from breaking sincethere is no thinner portion unlike in the sealing device in theconventional art and, furthermore, leakage due to decrease of tighteningmargin hardly occurs.

Still furthermore, the first and the second sealing parts are simple inconstruction, and thus may be downsized and designed for space-saving incomparison with the construction of the sealing device having the seallip as in the conventional art.

Then, since it can be used even when the working pressure of thehigh-pressure fuel is as high as 0-2 MPa, the drain port can beeliminated and thus simplification of the pump construction is achieved.

Preferably, the first sealing part includes a seal retaining memberforming a side wall of a groove on the side of the mounting groove foraccommodating the first sealing part fitted therein opposite from theside to be sealed, and the seal retaining member is formed with a secondmounting groove for accommodating the second sealing part.

Accordingly, a seal of dual-sealing construction is formed with a simpleconstruction.

Preferably, the second sealing part is a squeeze packing.

Accordingly, improvement of sealing property is achieved.

Preferably, the second sealing part includes a resin sealing memberwhich comes into slidable sealing contact with one of the opposedsurfaces and an urging member for urging the resin sealing member towardthe one of the opposed surfaces.

Accordingly, usage of the device under higher pressure is realized.

Preferably, the second sealing part is a packing having a back-pressureleaking capability.

Accordingly, even when the pressure is accumulated between the firstsealing part and the second sealing part, the accumulated pressure canbe released through the packing having the back-pressure leakingcapability of the second sealing part, thereby the durability can beimproved.

Preferably, the second sealing part is a sealing member having a seallip portion which comes into slidable sealing contact with the one ofthe opposed surfaces.

Accordingly, the sealing property of the device can further be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing showing a sealing device according to a firstembodiment.

FIG. 2 is a half cross-sectional view showing a peripheral system towhich the sealing device according to the first embodiment is applied.

FIG. 3 is a drawing showing another example of the sealing deviceaccording to the first embodiment.

FIG. 4 is a drawing showing the sealing device according to the secondembodiment.

FIG. 5 is a drawing showing the sealing device according to the thirdembodiment.

FIG. 6 is a drawing showing the sealing device according to the fourthembodiment.

FIG. 7 is a drawing showing the sealing device according to the fifthembodiment.

FIG. 8 is a drawing showing the sealing device according to the sixthembodiment.

FIG. 9 is a half cross-sectional view showing a sealing device accordingto the related art.

BEST MODE FOR CARRYING OUT THE INVENTION

Referring now to the drawings, preferred embodiments of the presentinvention will be described in detail. However, dimensions, materials,configurations, and the relative positions thereof stated in theseembodiments are not limited thereto unless otherwise specifically noted.

First Embodiment

FIG. 1 shows a sealing device 1 according to a first embodiment, andFIG. 2 shows a peripheral system to which the sealing device 1 in FIG. 1is applied.

The sealing device 1 in FIG. 1 is used as a sealing device forreciprocating movement, which requires a high sealing property, to beused in a high-pressure fuel pump for pressurizing fuel to a highpressure in an engine of in-cylinder direct injection system thathigh-pressure fuel is directly injected in a cylinder for combustion,and is employed for seal the high-pressure fuel supplied on thehigh-pressure side H, which is to be sealed with respect to a axiallyreciprocating shaft 10.

In FIG. 1, the sealing device 1 is attached at the end of a housing 11for sealing a high-pressure fuel (gasoline, light oil, and so on), whichis to be sealed, supplied from the high-pressure side H from passing asliding portion of a shaft guiding portion of the housing 11. Besides,on the low-pressure side L of the sealing device 1, oil for lubricationand cooling is sealed.

The sealing device 1 includes a first sealing part 2 and a secondsealing part 3 arranged in this order from the high-pressure side H atthe end portion of the housing 11 having an enlarged inner diameter.

A mounting groove for accommodating the first sealing part 2 fittedtherein is formed in such a manner that a shoulder portion formed byenlarging the inner diameter at the end of the housing 11 is defined asa sidewall of a groove on the high-pressure side, and a seal retainer 4which serves as seal retaining member is disposed on the low-pressureside L.

The first sealing part 2 to be fitted in the mounting rove includes aresin ring 21, which is a sealing member formed of resin, coming intoslidable sealing contact with the shaft 10, and an O-ring 22, which isan urging member for urging the resin ring 21 toward the shaft 10.

The resin ring 21 of the first sealing part 2 is annular shape having arectangular cross-section, and is formed of a resin material oftetrafluoroethylene group. Using such material contributes to achieveproperties superior in fuel resistance, heat resistance, abrasion proof,and slidability. The inner peripheral surface of the resin ring 21defines a sliding surface which comes into abutment with/slides over theshaft 10.

The O-ring 22 is formed of rubber-like resilient body disposed on thebackside, the side of the housing 11 (on the bottom side of the groove),of the resin ring 21. The resin ring 21 is urged toward the shaft 10 byan urging force generated as a reaction of the O-ring 22 when beingcrushed in the radial direction. The O-ring 22 is formed of fluorinatedrubber, acrylic rubber, or the like. Using such material contributes toachieve properties superior in fuel resistance and heat resistance.Preferably, fluorinated rubber, which is superior also in lowtemperature resistance (For example, Viton GLT from Dupont), is used.

On the other hand, the seal retainer 4 forming a side wall of a grooveon the low-pressure side of the mounting groove for accommodating thefirst sealing part 2 fitted therein is a ring-shaped member formed ofmetal or the like to be fitted in the inner periphery at the end of thehousing 11 of enlarged diameter. A second mounting groove for fittingthe second sealing part 3 is formed on the inner periphery of the sealretainer 4.

In the second mounting groove of the seal retainer 4, the second sealingpart 3 is fitted so that sealing on the low-pressure side L is achievedby being abutted to and sliding on the shaft 10.

The second sealing part 3 uses an X-ring 31, which is a squeeze packing.Incidentally, the squeeze packing used in the second sealing part 3 maybe an O-ring, a D-ring, and the like. Material of the squeeze packing isfluorinated rubber or acrylic rubber which is superior in fuelresistance and heat resistance. Preferably, fluorinated rubber is used.

The sealing device 1 thus constructed is applied to a system as shown inFIG. 2. That is, in FIG. 2, the shaft 10 moves reciprocally by therotation of a cam 5 connected directly to the engine, and increases thepressure of the high-pressure fuel on the high-pressure side H. Thespring 6 keeps the shaft 10 constantly in contact with the cam 5 so thatthe operation of the cam 5 is connected directly to the shaft.

Here by setting the distance between the first sealing part 2 and thesecond sealing part 3 longer than the reciprocating stroke of the shaft10, entry of a fluid to be sealed in the first sealing part 2 into thesecond sealing part can be prevented. On the other hand, by setting thedistance between two lips of the X-ring 31 which come into contact withthe shaft 10 shorter than the reciprocating stroke of the shaft 10,lubricating oil spreads over both lips, and thus lubricity is maintainedand abrasion of the lips is reduced, whereby the life of the lips can beincreased.

The sealing device 1 in this arrangement has a dual-sealing constructionin which the high-pressure fuel on the high-pressure side H is sealed bythe first sealing part 2, oil such as engine oil coming from the cam 5side on the low-pressure side L is sealed by the second sealing part 3,and slight leakage of the high-pressure fuel due to failure of scrapingat the first sealing part 2 can be sealed at the second sealing part 3.

Therefore, the sealing device 1 according to the present embodiment canbe used at the working pressure of 0-2 MPa and is prevented frombreaking even when being subjected to the pressure of the high-pressurefuel at 5 MPa or higher.

In addition, since the resin ring 21 which comes into slidable sealingcontact with the shaft 10 is used in the first sealing part 2, even whenfuel having less lubricity is used, abnormal abrasion is prevented andthus durability of the seal is improved.

Furthermore, since the resin ring 21 is used at the first sealing part2, swelling hardly occurs even when a fuel containing alcohol is used.The O-ring 22 is prevented from breaking since there is not thinnerportion unlike in the sealing device in the conventional art and leakagedue to decrease of tightening margin hardly occurs.

Still furthermore, the first and the second sealing part 2, 3 are simplein construction, and thus may be downsized and designed for space-savingin comparison with the construction of the sealing device having theseal lip as in the conventional art.

In addition, since it can be used even when the working pressure of thehigh-pressure fuel is as high as 0-2 MPa, the drain port can beeliminated and thus simplification of the pump construction is achieved.

Incidentally, in this embodiment, the resin ring 21 of the first sealingpart 2 is a rectangle in cross section. However, it is not limitedthereto, and resin rings 23, 24 having cross sections shown in FIG. 3may be employed. The resin ring 23 shown in FIG. 3( a) has a taperedsurface on the low-pressure side L with the axial center of the slidingsurface projected. The resin ring 24 shown in FIG. 3( b) has a taperedsurface on the sliding surface on the high-pressure side H so as todeviate from the shaft as it get close to the high-pressure side.Accordingly, distribution of the sealing surface pressure seals thefluid to be sealed on the high-pressure side H, and the pressureaccumulated between the first sealing part 2 and the second sealing part3 can be discharged toward the high-pressure side H.

Moreover, mounting the sealing device can be performed easily by firstlypressing the resin ring 21 and the O-ring 22 which constitute the firstsealing part 2 to the side wall of a groove of the mounting groove onthe high-pressure side, and then fitting the seal retainer 4 to thehousing 11 with the X-ring 31 which constitutes the second sealing part3 fitted in the seal retainer 4.

Second Embodiment

FIG. 4 is a half cross-sectional view showing the sealing device 1according to the second embodiment. Incidentally, since theconfiguration, material and the like of each member are the same asthose in the first embodiment, description will be omitted.

In the sealing device 1 shown in FIG. 4, the second sealing part 3includes a second resin ring 32 that comes into slidable sealing contactwith the shaft 10 which is similar to the first sealing part 2, and asecond O-ring 33 for urging the second resin ring 32 toward the shaft10.

In this arrangement as well, the same effects as the first embodiment isachieved. Moreover, with the second sealing part 3 of this construction,durability against the high-pressure increases and thus usage of thedevice under higher pressure is realized.

Third Embodiment

FIG. 5 is a half cross section showing the sealing device 1 according tothe third embodiment. Incidentally, since the configuration, material,and the like are the same as those in the first embodiment other thanthat the seal retainer 4 is not used, description will be omitted.

In the sealing device 1 shown in FIG. 5, a U-packing 34. is used as apacking having a back-pressure leaking capability for the second sealingpart 3. The packing having the back-pressure leaking capability used forthe second sealing part 3 is not limited to the U-packing 34, and othertypes of packing may be used. Material to be used for this packing isfluorinated rubber or acrylic rubber, which are superior in fuelresistance and heat resistance. Preferably, fluorinated rubber is used.

In the construction described above as well, the same effects as in thefirst embodiment are achieved. Also, even when the pressure isaccumulated between the first sealing part 2 and the second sealing part3, the accumulated pressure may be released toward the low-pressure sideL from the U-packing 34 of the second sealing part 3, thereby durabilitycan be improved.

Here, the mounting groove for accommodating the first sealing part 2fitted therein in this embodiment is divided at the portion indicated bya line A. Therefore, it is possible to divide the housing 11 at theportion of line A for fitting the resin ring 21 and the O-ring 22 of thefirst sealing part 2. The resin ring 21, which can hardly be deformed,and the O-ring 22 can be attached easily.

In addition, according to the present embodiment, the distance betweenthe positions where the first sealing part 2 and the second sealing part3 are disposed is set longer than the reciprocating stroke of the shaft10, and thus fuel can hardly reach the second sealing part 3, therebyentrance of fuel into the second sealing part 3 is prevented.

Fourth Embodiment

FIG. 6 is a half cross-sectional view showing the sealing device 1according to the fourth embodiment. Incidentally, since theconfiguration, material, and the like are the same as those in the thirdembodiment, description will be omitted.

In the sealing device 1 shown in FIG. 6, the second sealing part 3includes oil seals 35, 36 as sealing members each having a seal lipportion. The oil seal 35 is disposed on the high-pressure side H and theoil seal 36 is disposed on the low-pressure side L.

The oil seals 35, 36 are both constructed by attaching a rubber-likeresilient body on a metal ring by baking. Material of the rubber-likeresilient body used is fluorinated rubber or acrylic rubber which issuperior in fuel resistance and heat resistance for the both oil seals35, 36. Preferably, fluorinated rubber is used. Also, the tip of theinner diameter of the metal ring of the oil seal 35 on which the seallip portion is attached by baking is set as small as possible, so as toprevent deformation of the seal lip portion and the pressure resistanceis improved.

The seal lip portions of the respective oil seals 35, 36 are pressedagainst the surface of the shaft 10 by a garter spring.

The distance between the tips of seal lip portions of the oil seals 35,36 is set shorter than the reciprocating stroke of the shaft 10, andthus lubricating oil spreads over the both oil seals 35, 36.

Here, the seal lip portion of the oil seal 35 extends toward thehigh-pressure side H. It is for sealing leakage of fuel on thehigh-pressure side H sufficiently by the oil seal 35. The seal lipportion of the oil seal 35, which comes into contact with the surface ofthe shaft 10, is arcuate shape at the tip thereof. The arcuate shape canlower the sliding resistance with respect to the surface of the shaft10, so that abrasion is prevented even when sliding especially withfuel, and leakage of oil supplied from the low-pressure side L via thesurface of the shaft 10 due to failure of scraping is prevented.

In addition, the seal lip portion of the oil seal 36 extends toward thelow-pressure side L. It is for sealing leakage of oil on thelow-pressure side L.

Here, the oil seal 35 is covered at the fitting portion with therubber-like resilient body to achieve rubber fitting for preventingleakage. Also, the oil seal 36 is constructed at the fitting portion ofonly the metal ring to achieve metal fitting for fixing the oil seals35, 36.

In the construction described above, the same effects as the firstembodiment are achieved. Moreover, since the oil seals 35, 36 having theseal lip portions for the second sealing part 3 are used, sealingproperty of the device is further improved.

In this embodiment as well, the mounting groove for accommodating thefirst sealing part 2 fitted therein can be divided at the portionindicated by the line A as in the case of the third embodiment. Also,the distance between the positions where the first sealing part 2 andthe second sealing part 3 are disposed is set longer than thereciprocating stroke of the shaft 10. The effect thereof is as describedin conjunction with the third embodiment.

Fifth Embodiment

FIG. 7 is a half cross-sectional view showing the sealing device 1according to the fifth embodiment. Incidentally, since theconfiguration, material and the like of each member are the same asthose in the third embodiment, description will be omitted.

The sealing device 1 in FIG. 7 employs an oil seal 37 as a sealingmember having a seal lip portion for the second sealing part 3. Inaddition, a sub packing 38 as auxiliary sealing member is disposed onthe high-pressure side H of the oil seal 37.

The oil seal 37 is constructed by attaching a rubber-like resilient bodyon a metal ring by baking. Material to be used for the rubber-likeresilient body is fluorinated rubber or acrylic rubber, which aresuperior in fuel resistance and heat resistance. Preferably, fluorinatedrubber is used. The oil seal 37 is mounted using the metal ring fittedaround the outer periphery of the housing 11.

The seal lip portion of the oil seal 37 is pressed against the surfaceof the shaft 10 by a garter spring.

The seal lip portion of the oil seal 37 extends toward the low-pressureside L. It is for sealing leakage of oil on the low-pressure side L bythe oil seal 37.

The sub packing 38 is a U-packing or the like disposed in a squaremounting groove on the high-pressure side H with respect to the oil seal37, and the outer peripheral surface of the packing is provided with aprojection for increasing the surface pressure and thus improving thesealing property. The inner peripheral surface of the sub packing 38 cansufficiently seal leakage of fuel on the high-pressure side H by slidingon the shaft 10. Furthermore, since the housing 11 is positioned asclose to the shaft 10 as possible on the low-pressure side L, the subpacking 38 is prevented from being deformed and thus pressure resistanceis improved. The same material as the rubber-like resilient body of theoil seal 37 is used for the sub packing 38 as well.

In the construction described above as well, the same effects as in thefirst embodiment are achieved. Moreover, since the oil seal 37 and thesub packing 38 having the seal lip portions are used for the second sealpart 3, further improvement of the sealing property of the device isachieved. In addition, since the compact oil seal 37 is used, the axialdimension of the device may be reduced.

Incidentally, in this embodiment as well, the mounting groove foraccommodating the first sealing part 2 fitted therein may be divided atthe portion indicated by the line A as in the case of the thirdembodiment. Also, the distance between the positions where the firstsealing part 2 and the second sealing part 3 are disposed is set longerthan the reciprocating stroke of the shaft 10. The effects thereof arethe same as described in conjunction with the third embodiment.

Sixth Embodiment

FIG. 8 is a half cross-sectional view showing the sealing part 1according to the sixth embodiment. Incidentally, since theconfiguration, material, and the like are the same as those in the thirdembodiment, description will not be made.

In the sealing device 1 in FIG. 8, an oil seal 39 is employed as asealing member having a seal lip portion for the second sealing part 3.

The oil seal 39 is constructed by attaching a rubber-like resilient bodyon a metallic ring by baking. Material to be used for the rubber-likeresilient body is fluorinated rubber or acrylic rubber, which aresuperior in fuel resistance and heat resistance. Preferably, fluorinatedrubber is used. The oil seal 39 is mounted using the metal ring fittedaround the outer periphery of the housing 11 to achieve metal fittingfor enhancing the fitting force. Here, an O-ring 39 a is interposedbetween the metal ring of the oil seal 39 and the housing 11. It is forpreventing leakage at the metal fitting portion by the C-ring 39 a.

The seal lip portion of the oil seal 39 extends separately toward thehigh-pressure side H and the low-pressure side L, and the respectiveportions are pressed against the surface of the shaft 10 by the garterspring.

Since the seal lip portion of the oil seal 39 extends separately towardthe high-pressure side H and the low-pressure side L, the material ofthe rubber-like resilient body may be well distributed to the two seallip portions when fabricating by providing the tip of the innerperiphery of the metal ring at the root on which the rubber-likeresilient body is attached by baking with a plurality of recesses formedby setting down the tip portion thereof in the circumferential directionor by providing a plurality of holes in the circumferential direction sothat the area passing therethrough is extended on both sides.

The seal lip portion extending toward the high-pressure side H of theoil seal 39 sufficiently seals leakage of fuel on the high-pressure sideH. The seal lip portion extending toward the high-pressure side H has anarcuate shape at the tip portion of the lip that comes into contact withthe surface. of the shaft 10. This arcuate shape can reduce slidingresistance with respect to the surface of the shaft 10, so that abrasioncan be prevented even when sliding especially with fuel. In addition,leakage of oil supplied from the low-pressure side L via the surface ofthe shaft 10 due to failure of scraping is prevented.

In addition, the seal lip portion extending toward the low-pressure sideL of the oil seal 39 seals leakage of oil on the low-pressure side L.

In the construction described above as well, the same effects as in thefirst embodiment are achieved. Moreover, since the oil seal 39 havingthe seal lip portion for the second sealing part 3 is used, sealingproperty of the device is further improved.

Incidentally, in this embodiment as well, the mounting groove foraccommodating the first sealing part 2 fitted therein can be divided atthe portion indicated by the line A as in the case of the thirdembodiment. Moreover, the distance between the positions where the firstsealing part 2 and the second sealing part 3 are disposed is set longerthan the reciprocating stroke of the shaft 10. The effect thereof is asdescribed in conjunction with the third embodiment.

INDUSTRIAL APPLICABILITY

As described above, according to the present invention, since the firstsealing part and the second sealing part disposed on the side of thefirst sealing part opposite from the portion to be sealed are provided,a dual-sealing structure in which slight leakage due to failure ofscraping at the first sealing part is sealed by the second sealing partis realized. Therefore, it can be used at the working pressure of 0-2MPa, and moreover, it is prevented from breaking even when beingsubjected to the pressure of the high-pressure fuel at 5 MPa or higher.

Also, since the resin sealing member, which comes into slidable sealingcontact with the one of the opposed surfaces, is used in the firstsealing part, even when fuel having less lubricity is used, abnormalabrasion is prevented and thus durability of the seal is improved.

In addition, even when fuel containing alcohol is used, swelling hardlyoccurs at the first sealing part since the sealing member used is madeof resin, and the urging member is prevented from breaking since thereis no thinner portion unlike in the sealing device in the conventionalart and, furthermore, leakage due to decrease of tightening marginhardly occurs.

Furthermore, the first and the second sealing part are simple inconstruction, and thus may be downsized and designed for space-saving incomparison with the construction of the sealing device having the seallip as in the conventional art.

Then, since it can be used even when the working pressure of thehigh-pressure fuel is as high as 0-2 MPa, the drain port can beeliminated and thus simplification of the pump construction is achieved.

Also, since the seal retaining member forming a side wall of a groove onthe side of the mounting groove for accommodating the first sealing partfitted therein is provided opposite from the side to be sealed, and theseal retaining member is formed with a second mounting groove foraccommodating the second sealing part, a seal of dual-sealingconstruction is formed with a simple construction.

Since the second sealing part is a squeeze packing, improvement ofsealing property is achieved.

Since the second sealing part includes the resin sealing member whichcomes into slidable sealing contact with one of the opposed surfaces andthe urging member for urging the resin sealing member toward the one ofthe opposed surfaces, usage of the device under higher pressure isrealized.

Since the second sealing part is the packing having the back-pressureleaking capability, even when the pressure is accumulated between thefirst sealing part and the second sealing part, the accumulated pressurecan be released through the packing having the back-pressure leakingcapability of the second sealing part, thereby the durability can beimproved.

Since the second sealing part is the sealing member having the seal lipportion which comes into slidable sealing contact with the one of theopposed surfaces, the sealing property of the device can further beimproved.

1. A fuel pump comprising: a housing, a reciprocating shaft located inthe housing, a sealing device for sealing an annular gap formed betweenthe reciprocating shaft and the housing, said sealing device including asealing part including a resin sealing member coming into slidablesealing contact with a surface of the shaft, and an urging member forurging the resin sealing member toward the surface of the shaft, thesealing part sealing the side to be sealed where fuel exists, and asqueeze packing disposed on the side of the sealing part opposite to theside to be sealed for sealing fuel depressurized at the sealing part andlubrication oil which exists on the opposite side of where fuel exists,a distance between the sealing part and the squeeze packing being longerthan a reciprocating stroke of the shaft to prevent the fuel sealed bythe sealing part from entering the squeeze packing, and the squeezepacking being a U-packing.
 2. A fuel pump comprising: a housing, areciprocating shaft located in the housing, a sealing device for sealingan annular gap formed between the reciprocating shaft and the housing,said sealing device including a first sealing part located in a steppedportion at an end of the housing, said first sealing part including afirst resin sealing member in sliding sealing contact with a surface ofthe shaft; and a first urging member for urging the first resin sealingmember toward the surface of the shaft, the first sealing part sealing ahigh pressure side to be sealed where fuel exists between the housingand the shaft, a second sealing part disposed in the stepped portion atan end of the housing on a side of the first sealing part opposite tothe side to be sealed for sealing fuel between the housing and theshaft, the second sealing part including a sealing member sealing a lowpressure side to be sealed where oil exists between the housing and theshaft, and a seal retainer having a recess for accommodating the sealingmember of the second sealing part, and the seal retainer having asurface defining an accommodating space for accommodating the firstsealing part between the surface of the seal retainer and a surface ofthe stepped portion of the housing.
 3. A fuel pump comprising: ahousing, a reciprocating shaft located in the housing, a sealing devicefor sealing an annular gap formed between the reciprocating shaft andthe housing, said sealing device including a sealing part including aresin sealing member coming into slidable sealing contact with a surfaceof the shaft, and an urging member for urging the resin sealing membertoward the surface of the shaft, the sealing part sealing a side to besealed where fuel exists, and oil seals disposed on a side of thesealing part opposite to the side to be sealed for sealing fueldepressurized at the sealing part, the oil seals being a rubber-likeresilient body on a metal ring.
 4. The pump according to claim 3,wherein the oil seals are mounted using the metal ring fitted around anouter periphery of the housing.
 5. The fuel pump according to claim 4,further comprising a U-packing disposed on the side to be sealed of theoil seals.
 6. The pump according to claim 3, wherein the oil seals aremounted using the metal ring fitted around an inner periphery of thehousing.
 7. The fuel pump according to claim 3, wherein the oil sealsinclude two oil seals that are mounted using the metal ring fittedaround an inner periphery and outer periphery of the housing,respectively, and a distance between tips of seal lip portions of bothof the oil seals is shorter than a reciprocating stroke of the shaft,and thus lubricating oil spreads over both of the oil seals.
 8. The fuelpump as claimed in claim 2, wherein said second sealing part includes asecond resin sealing member in sealing contact with the surface of theshaft and the second resin sealing member is urged by a second urgingmember toward the surface of the shaft.
 9. The fuel pump as claimed inclaim 8, wherein said seal retainer surrounds said second urging memberon three sides.
 10. The fuel pump as claimed in claim 2, wherein saidfirst resin sealing member is a ring having opposite identical flatsurfaces with one of said flat surfaces in contact with said shaft. 11.The fuel pump as claimed in claim 9, wherein said second resin sealingmember is a ring.
 12. The fuel pump as claimed in claim 9, wherein saidseal retainer is U-shaped.